Manchester United fans will have a chance to witness on Sunday how far a Glazer-owned team can fall once the family tightens the purse strings.

As the supporters watch United's match at Anfield dreaming of a fourth straight Premier League title, the Glazer-owned Tampa Bay Buccaneers will be at Wembley preparing to face the New England Patriots and hoping against the odds to win their first NFL game of the season after six straight losses.

It has been a painful slide from the lofty days of February 2003 when the Buccaneers won the Super Bowl and Malcolm Glazer was the toast of Tampa.

Message boards in Florida are full of comments from fans who blame the family's acquisition of United and the size of the debt repayments as the reason for the slump, says Jim Flynn, editor-in-chief at Pewter Report, a large online community of Bucs fans. There are calls for the Glazers to sell up if they don't want to invest in players.

A typical entry on one of the many fan forums comes from Joe Rauner, of Tampa, who wrote: "The day the Glazers bought Manchester United, the Bucs started to go downhill. Thirty million under the salary cap?! C'mon Glazers, get off your wallets and bring in some players."

The NFL salary cap is in place to try to ensure that all 32 teams can be competitive and have a chance of reaching the Super Bowl. The Glazers have not spent around $30 million of this year's $128m cap allowance, which is the highest under-spend in the league.

In the glory days at the beginning of the decade, the Glazers spent lavishly to bring in big-name players and even gave the Oakland Raiders $8m and four high player draft picks to snatch away their coach John Gruden.

Those days are long gone. Recently released statistics from the NFL show the Bucs, since the Glazers turned their attention to United, have spent less on new players than any other franchise.

Unsurprisingly, the Buccaneers have not come close to repeating their Super Bowl success. Gruden was sacked in the summer and replaced by novice Raheem Morris, and the team, with a few exceptions, is inexperienced.

While Sir Alex Ferguson says he has all the money he needs at Old Trafford, the Tampa Bay situation should give fans reason to pause for thought about what might happen if the club's debt situation becomes unmanageable.

At Old Trafford, the debt which was £660million after a 2006 refinancing now stands at £699m, which certainly caused Martin Edwards, the chairman from 1980 to 2002, to pause, think and express his doubts.

"It concerns me that the club are in so much debt," Edwards said. "The club are not in control. The [Glazer] family are in control of the debt.

"The crunch time will come when they [the Glazers] exit. Will they saddle the club with the debt or just sell the club on for a profit because that's all they are interested in? How will they leave the club?"

There is no sign of the Glazers quitting either club. And why should they as their investments look very profitable - at least on paper.

According to Forbes magazine, United's value has more than doubled since they bought the club. It is now worth $1.97billion, or £1.2bn at today's exchange rates.

The Glazers' investment in Tampa has also paid off handsomely. The family paid $192m for the team in 1995 and it is now valued at $1.1bn, proving that having a winning team is not essential to financial success.

The Glazers do have their supporters among Tampa fans. One is Paul Stewart, who founded the Bucs UK fan club and runs the Bucpower.com web site from Staines in Surrey. He attributes the lack of success to a "rebuilding year" caused because the Gruden regime "left the cupboard bare."

He disagrees empathetically that owning Manchester United has caused the Glazers to ignore the Bucs. "The funny thing is everyone in America thinks they are spending all their money on Manchester United and everyone over here thinks they are spending their money on the Bucs and ignoring Manchester United. They can't win."